1. Field of the Invention
The invention relates to an electronic component for assembly on the surface of a printed-circuit board, especially a power transistor for high-frequency applications.
2. Description of the Related Art
Electronic components, especially power transistors, which are mounted on the surface of a printed-circuit board, are already known. If these components must be cooled during operation, a mounting, by means of which a cooling element can be attached to the component, must be provided on the component in addition to the contact surfaces of the component. A high-frequency power transistor with a synthetic-material housing is known, for example, from the technical datasheet “MRF 1535T1/D”, Motorola Inc. Connecting elements of the transistor are guided laterally outwards from the synthetic-material housing and folded in the direction of the side of the component facing towards the printed-circuit board. A contact surface is formed on each of the folded ends of the connecting elements, so that the component can be fitted onto the surface of a printed-circuit board. A flat surface, which can be brought into contact with a cooling element, is provided on the opposite side of the component, and a part of the housing of the component is formed on the side of the component facing away from the printed-circuit board. In order to attach the cooling element to this contact surface, recesses are provided in the transistor housing, which is made from synthetic material, by means of which the transistor and the cooling element can be bolted jointly to the printed-circuit board.
A folding of the connecting elements is disadvantageous, especially for applications in the high-frequency range. The curved geometry of the connecting elements generates a high parasitic inductivity and possibly also parasitic capacity, which reduce the useful frequency range. Furthermore, as a result of the relatively small contact surface between the cooling element and the transistor, a special cooling element is required in order reliably to remove the quantity of heat occurring during the operation of a power transistor of this kind. Moreover, this special cooling element must be attached directly to the component housing to ensure good thermal transfer.